1. Field of the Invention
The present invention relates to a door mirror assembly for automotive vehicles. More particularly, the invention relates to improvements in the support relationship between a mirror body side member of the mirror assembly and a strut formed in the vehicle side member thereof.
2. Description of the Prior Art
A door mirror, assembly for automotive vehicles has a case rotatably supported on the strut of a vehicle side member and a mirror body fixed to the case. The construction will be explained more concretely with reference to FIG. 10 showing an example disclosed in the specification of Japanese Utility Model Application Laid-Open (KOKAI) No. 60-179545. A lower case 3 is rotably supported on a strut 2 of a vehicle side member 1. The lower case 3 is integrally formed with a frame 5 on which a mirror control actuator unit can be mounted, while an upper case 4 is fixed to the lower case 3. A mirror body 6 is fixed to the cases 3, 4 and the frame 5. Arranged in the upper case 4 are a motor 7 and reduction gears 8, a final gear 9 of which is held in meshing engagement with a driving gear 10 supported on the strut 2. The driving gear 10 is connected to a torque limiter 12 subjected to the biasing force of a spring 11, one end of which is seated on the inner wall of the lower case 3. When a large external force acts on the mirror body 6, the torque limiter 12 slides. Therefore, the position of the mirror body 6 can be manually changed.
The motor 7 rotates when energized. The rotation of the output shaft of the motor 7 rotates the final gear 9 after being decelerated by the reduction gears 8. The rotation of the final gear 9 attempts to rotate the driving gear 10 meshing with this final gear. However, since the driving gear 10 is held fixed on the strut 2 by the torque limiter 12, the gear 10 is not rotated and the final gear 9 revolves around it. As a result, the cases 3, 4, frame 5 and body 6 turn about the strut 2 in unison. The mirror body 6 can be tilted in the lateral and vertical directions by the actuator unit disposed in the frame 5, but the tilting operation need not be described here.
A ball 13 is embraced by the vehicle side member 1 and the lower case 3 and is effective for positioning the lower case 3 relative to the vehicle side member 1 and for obtaining smooth motion.
The prior-art assembly has a first problem described hereinbelow. Specifically, as seen in FIG. 10, the holding length L.sub.1 of the lower case 3 for the strut 2 is small. Therefore, the image in the mirror is likely to move due to vibration caused by air while the vehicle is traveling at high speed or to vibration caused by traveling on a bad road. Moreover, in the event that an overload acts in the turning direction or vertical direction of the mirror body, stresses concentrate in the bearing portion of the lower case 3 of strut 2, as a result of which this portion is damaged.
In particular, in a door mirror assembly as shown in FIG. 1 in which a space A for preventing noise caused by wind is provided between a vehicle side member 21 and a mirror body 28, the axis of the mirror is likely to shift to the right as viewed in the figure, thereby aggravating the aforementioned drawbacks.
The second problem of the prior-art assembly is as follows: In recent mirror assemblies, the space indicated at A in FIG. 1 is provided for the purpose of reducing air resistance and noise caused by the mirror assembly cutting through the air when the vehicle is traveling. However, the provision of the space A decreases the mounting space inside the mirror body 28. Inevitably, it causes the strut, reduction gears and mirror actuator to be moved to sideward outer positions and brings the position of the center of gravity of the assembly sideward, farther from the vehicle side member 21. Accordingly, an external force acting on the mirror assembly exerts a greater load on the holding portion between the case and the strut of the vehicle side member and is likely to damage this portion.
The third problem of the prior-ar assembly is as follows: When the mirror body 6 is turned manually or by the motor 7 in the prior-art example shown in FIG. 10, the lower case 3 is moved relative to the vehicle side member 1 through the nodal ball 13. The lower case 3 moves up and down until the ball enters the next nodal hole. That is, while the ball is being transferred from one nodal hole to the next, the mirror assembly moves vertically. Of course, the vertical motion is resiliently absorbed by the spring 11 so that the mirror assembly will not rattle. However, a clearance is required in the height direction of the mirror assembly to allow the vertical motion, so that an object cannot be disposed in the vicinity of the mirror assembly.